Figure 13.

Simple electrolysis cell‐design (A) uses two cation‐exchange membranes (blue) to create three compartments. In the anodic compartment, the oxygen evolution reaction on the anode produces protons and oxygen. The protons migrate to the middle compartment, where they exchange potassium for a proton to form oxalic acid. The potassium migrates through the cation‐exchange membrane to the cathodic compartment, where it forms potassium hydroxide with the hydroxide ions produced on the cathode during the hydrogen evolution reaction. In the advanced multifunctional cell (B), which has the fourth compartment by adding a bi‐polar membrane, the salt splitting can be coupled with the production of high‐value chemicals. A reductant is reduced in the cathodic compartment and an oxidant is oxidized in the anodic compartment. The proton for the reduction is drawn from the bipolar membrane in which water splitting is taking place.